1. Field of the Invention
The present invention relates to the technical field of image processing and, more particularly, to an image processing device and method for reducing color artifact.
2. Description of Related Art
In a DVB-T system or a cable-imaging system, a front tuner needs to modulate an image signal from radio frequency into baseband. During the process of modulation, filtering is executed in the frequency domain to avoid aliasing. But, there are overshooting, undershooting, and ringing effect to image signals in the time domain.
In order to deal with the problems of overshooting, undershooting, and ringing effect, a low pass filter is usually used to reduce the artifact in the conventional image processing techniques. FIG. 1 is a diagram of the Cr signal in the boundary between white (Cr value=0) and yellow (Cr value=20). As shown in FIG. 1, when the Cr value is equal to 0, it means that the color component of Cr is the smallest. The circle in FIG. 1 shows the artifact owing to undershooting (Cr value<0) occurs, and then results in an exceeded color boundary in images. The processing method of the conventional techniques is to use a low pass filter to reduce the artifact. As shown in FIG. 2, it is the result of passing through a low pass filter. FIG. 3 is a diagram about overlapping the results of the two signals without and with passing through a low pass filter. It is known from FIG. 3 that after the filtering process, undershooting of the signal is reduced. But the range of undershooting in FIG. 3 becomes larger. Namely, using low pass filters causes the light-color area of the original signal to have stronger color, so that the artifact of color bleeding in the image is induced. The artifact, mainly in the boundary between different colors, causes an image, which is in gray level originally, to have other colors after the filtering process. Such as the problem of color bleeding has green (in the undershooting area) in the boundary between white and yellow.
The conventional image processing techniques generally use filters for reducing overshooting, undershooting, and ring effect, but the artifact of color bleeding is not considered. Thus, it is desirable to provide an improved image processing device and method to mitigate and/or obviate the aforementioned problems.